This invention relates to a valve device having a pressure port connected to a pump; a first user port which is in communication with a pressure accumulator and a first user component and connectible with the pressure port through a throttle and a check valve; and a second user port which is connectible with the pressure port through a by-pass valve, the by-pass valve having a by-pass piston whose effective surface adapted to be subjected to pressure in the opening direction connects with the pressure port and whose effective surface adapted to be subjected to pressure in the closing direction and extending into a control chamber connects with the pressure port through a throttle and an accumulator-pressure-responsive pilot valve when the accumulator pressure is below a predetermined limit, and connects with a return line when the accumulator pressure has reached the predetermined limit.
From German Pat. DE-OS No. 2,625,555 a valve device is known which includes a pressure port connected to a pump. A connection leads from the pressure port through a throttle and a check valve to a first user port, with a first closed-center user component and a pressure accumulator being in communication with the first user port.
Further, the pressure port is connectible with a second user port through a by-pass valve, the second user port connecting with a second open-center user component.
The by-pass valve includes a by-pass piston whose effective surface adapted to be subjected to pressure in the opening direction is connected to the pressure port. The by-pass piston's effective surface which is adapted to be subjected to pressure in the closing direction connects with a pilot valve operating in response to the accumulator pressure. Below a predetermined accumulator pressure, the effective surface subjected to pressure in the closing direction connects with the pressure port through the pilot valve and a throttle, and when the predetermined accumulator pressure is attained, it connects with an unpressurized return line through the pilot valve.
If it is desired to use the known valve device for supplying fluid to another, third, closed-center user component without the function of the existing valve components being adversely affected, the third user component would have to be connected to the first user port. To avoid damage to the accumulator, the fluid deliverable from the pressure port to the first user port is limited to a predetermined amount by the throttle, and, therefore, it is not possible to supply fluid from the first user port to a third user component requiring a large amount of fluid. Such a user component is, for example, an antiskid apparatus in an automotive vehicle.